There already exists rheology additives which are fatty acid diamides, used for mastic and adhesive compositions, in particular diamides based on 12-hydroxystearic acid. These diamides, which are provided in the form of a micronized powder having a mean particle size ranging from 5 to 20 μm, are organogelators, that is to say small organic molecules capable of gelling organic solvents of all types, even at relatively low concentrations by weight. In their medium, they are often arranged in the form of fibres, which explains their organogelating and rheology-modifying effect. The change from the form of a powder to the form of fibres in an organic medium is known as activation. This activation is obtained by high shearing at a temperature suited to the use.
These diamides make it possible to have good performances in mastics of “MS-Polymer®” type, which are hybrid polymers based on alkoxylated silane endings, or polyurethane/silanes technology, with blocked silane endings, but they are poorly suited to the technology of polyurethane compositions, in particular one-component polyurethane compositions, symbolized in abbreviation by “1K-PU”, where they may generate problems of stability of these mastics, with premature crosslinking and a limited pot life in use, rendering the composition unusable.
Additives such as treated silicas and polyureas exist as alternative routes.
However, silicas present problems of health and safety during the handling thereof because of the very fine dusts emitted into the atmosphere, the problems of performance, of reproducibility and of sedimentation, in comparison with organic additives, such as amides or polyureas. There exists a known alternative among “organic” additives which are polyureas, often developed to be measured by the formulators of polyurethanes themselves. The polyureas manufactured from isocyanates and amine have, on the other hand, the disadvantage of being difficult to control as additives in terms of structure, of the performances and of reproducibility of the said performances and of manufacture, which reproducibility is related to problems of solubility and of compatibility with the manufacturing or application medium, in view of the very cohesive structure of a urea bond. Such a urea-based rheology additive is described, for example, in U.S. Pat. No. 6,548,593.
The present invention is targeted at an additive “activatable” at low temperature in a formulation which is sensitive to nucleophiles, in particular polyurethane, such as 1K-PU but also 2K-PU, more particularly 1K-PU, which additive offers an effective rheological solution and makes it possible to retain the stability of the formulations which are sensitive to nucleophiles, in particular polyurethanes, more particularly 1K-PU mastics, or other compositions which are sensitive to nucleophiles. The main technical problem to be solved is thus the search for means which make it possible to retain the stability of the said sensitive formulations during storage. Subsequently, as regards the rheological performance related essentially to the activation process, this performance will depend on the choice of the temperature and of the plasticizer used as a function of the final application medium.
The present invention is targeted more specifically at compositions with amide additives which allow them to be used as organogelators and in particular as rheology additives in compositions of formulations which are sensitive to nucleophiles, without the disadvantages mentioned of the state of the art, while preventing the deterioration in the stability of the said compositions or a premature gelling (signifying here irreversible crosslinking).